The miracle of conception

Getting pregnant is much more than a biological process – once you know what actually has to happen for an egg to get fertilised you will understand why conception is often referred to as a “miracle”.

The chances of getting pregnant in any given cycle are really surprisingly low. According to some estimates, the odds of a healthy, optimum-aged and fertile couple conceiving are about one in five each month.

On average, 20% of all couples trying to get pregnant will not conceive in the first year of trying. Here are some other statistics:

25% of couples get pregnant in the first month of trying

60% will conceive within six months

80% are pregnant within a year

Why is it so hard to conceive?

It can seem like the human reproductive system wasn’t actually designed to make babies.

Throughout the attempted conception process there are all sorts of hurdles and obstacles to overcome, from hostile mucus and receptive eggs to wayward, sluggish or damaged sperm. Add to that a very small window of conception opportunity – just a few days a month – and it’s amazing we ever conceive at all.

In simple terms, a woman must be about to ovulate as the millions of sperm head off on their journey. But that’s paring down the process to its most basic explanation.

Sperm and egg: the great mismatch

Every day men’s bodies are flat out making millions of sperm in the hope that one of them may actually get the extremely rare chance to join with an egg.

A healthy man’s ejaculation contains more than 100 million sperm. Sounds a lot but less than 40% are considered “normal” at the outset of the journey, and many millions will die off, get lost or swim off in the wrong direction before getting anywhere near where the egg lays in wait.

Only about 50 sperm actually get to the place where the egg should be after navigating through the minefield that is the cervical mucus, the uterus and the fallopian tubes. And then they need to hope that this fussy egg is open for business.

The egg is only available for fertilisation between 12 and 24 hours per cycle although the few surviving health sperm can lie in wait for the egg for up to five days.

Finally, if all is optimal, one lucky sperm will get the chance to penetrate the egg and conception occurs, starting a whole new difficult ball game.

What happens next?

Following penetration of the sperm into the ovum, the egg is fertilised and becomes an embryo. However, cell division and implantation of the embryo must take place for conception to be successful. This is the process of the embryo attaching itself to the uterine wall or uterine lining and happens around six days after fertilisation.

Now this embryo needs to cling on to life – and the risk of miscarriage is at it’s highest immediately following implantation. It’s thought that up to half of all fertilised eggs do not survive with many ending in an “unnoticed miscarriage” which may appear to be a period.

It’s estimated that up to 20% of known pregnancies will end up miscarrying and a large proportion of these will occur in the first trimester.